Effect of Potted Media Mixtures on Rooting Ability of Stem Cuttings of F 1 Arabica Coffee Hybrid

In Ethiopia, multiplication and distribution of the released F1 hybrid coffee varieties for producers were constrained by the problems associated with methods of propagation. An experiment was conducted on propagation by cuttings using F1 hybrid coffee Ababuna with the objective to determine and select suitable potting media mixture to carry out rooting directly in polythene bags under low cost propagating structure. Five rooting media in a randomized complete block design with four replications and 30 cuttings per treatment was used. Data on percent rooting and other root and shoot parameters were collected and analyzed using analysis of variance (ANOVA). The result indicated that most of the parameters measured, except for shoot development, were significantly influenced by potting media types. Accordingly, rooting media composed of 3Ts + 1S and Ts+10cm Fw ss on which cuttings produced significantly higher percent of rooting, root number and length were recommended and further investigation focused on the remaining hybrids and combination of alternative factors was also suggested to come up with conclusive recommendation to obtain sufficient number of rooted cuttings.


INTRODUCTION
Arabica coffee has its primary centre of origin and genetic diversity in the high lands of South West Ethiopia (Wrigley, 1988;Bellachew et al., 2000).It is the most important and still the leading foreign exchange earning commodity crop of Ethiopia and grown in almost all regions of the country between altitudes ranging from 550m to 2600m a.s.l.under different management practices (Bayetta,1986).Though the country has immense coffee genetic diversity, the productivity is constrained by many factors among which lack of adequate distribution of improved coffee varieties to the majority of coffee producers.
It is well known that highly productive hybrids that combine different characteristics of interest such as high yield, disease resistant and insect pest tolerant and good physical and cup quality etc., are highly required to increase production and productivity at present time (Van der Vossen, 2001).Generally, to exploit the potential hybrid vigor expressed in Arabica coffee, many countries experienced in utilization of vegetative propagation, mainly rooting of cuttings (Oloyede et al., 2004).Vegetative propagation by rooting cutting for large scale planting, however, is constrained mainly, among others, by type of rooting media, type of propagation system and environmental (temperature, drainage, relative humidity etc.) conditions inside the propagating structures where cuttings are kept.
Different aspects of vegetative propagation of the two economically important coffee species have been studied and the results however, are inconsistent indicating that there is no universally recommended method to be used (Wamatu and King'oro,1992;Mawardi and Purwadi, 2004;Oloyede et al., 2004).
In Ethiopia three F1 hybrid coffee varieties that yield 23-26qt clean coffee ha -have been released since 1977 (Bayetta et al., 1998).Propagation of these hybrid varieties by seed through hand emasculation and pollination of the complimentary parental lines has not been able to satisfy the increasing demand of the coffee farmers.Thus, largescale commercial production of hybrid coffee is not yet started and the producers could not benefit from the genetic potential of the varieties.
Studies on vegetative propagation to supplement the hybrid seed production were started at Jima Agricultural Research Center (JARC) in 2000 using Lyamungu type of mist propagation system.Accordingly, 89% rooting was obtained from soft wood stem cuttings when propagated using rooting media composed of top soil + sand + manure in 2:2:1 ratio (Behailu et al., 2004).However, the success rate of the rooted cuttings that reach to field transplanting was reduced to 60% due to death of the rooted cuttings after they have been transplanted to the recommended nursery potted media.This might be due to transplanting shock and during subsequent hardening off process.In addition the mist propagation system was found to be costly and unaffordable to be implemented at small-scale farmers level to facilitate the multiplication and the distribution of hybrid seedlings for large scale planting.
On the other hand, different authors have reported several alternatives, where sufficient propagules can be achieved among which, the use of closed non-mist propagator made from locally available materials and rooting cuttings by inserting directly in the pot filled with various mixtures of rooting media (Wood, 1985;Leakey et al., 1990;Coste, 1991).
However, such techniques of vegetative propagation had not been practiced under our condition.Therefore it is of paramount importance to study the rooting response of cuttings of F 1 hybrid coffee when directly inserted in potted media mixture and placed under non-mist propagator before considering effects of many factors at once.Thus, the present study was undertaken to determine and select suitable potting media mixture that insure sufficient rooting and growth of stem cuttings of F 1 hybrid coffee using non-mist propagator made from locally available materials.

Experimental design and treatments
The experiment was conducted in Ethiopia at Melko-Jima, the national coffee research center.In this experiment five rooting media composed of 2Ts + 2S + 1M (recommended media for mist propagation system), 6Ts + 3S + 2M (recommended nursery potting media), Ts + 10 cm filled with sub soil, 3Ts + 1S and 3Ts + 1S + 1M were tested to see their effect on rooting ability of stem cuttings of F 1 Arabica coffee hybrid (Aba buna).Each media filled into the black polythene bags with a 10 cm diameter and 25 cm length and arranged in Randomized Complete Block Design (RCBD) with four replications and 30 cuttings per treatment.

Propagator Construction
Four nursery beds each with 4.50 m length and 1.20 m width were prepared, leveled and raised 10 cm from the ground surface to put the polyethylene bags.Then, a non-mist propagator was constructed over the nursery bed from wooden frames.Artificial shade supported with wooden poles was constructed at the height of two meters above the ground level and covered with napper grass in such a way to allow 25 -35 % light intensity and protect falling of direct sun light on the cuttings.To create convenient working environment, 60 cm space was left between the poles and the propagator.

Preparation and planting of cuttings
Soft wood stem cuttings were prepared from Aba-buna F1 Coffee hybrid following procedures described by Wamatu (1993).Finally, they were inserted/planted directly into the poly bags to a depth of 4-5 cm, watered thoroughly and then, covered with a 30 microns thick white plastic sheet suspended over the wooden framework.The edge of the plastic sheet was buried in all direction so as to avoid evaporation of water from the rooting media and to maintain the required temperature and high relative humidity inside the propagator.Hand water application was done after one month depending upon the fine water droplets (water condensation) retained on the covering plastic sheet.Removal of weed, dead and diseased cuttings and other important management activities were carried out when necessary throughout the experimental period.

Data Collection and Analyses
After six months of planting, all live (including green but without shoot) cuttings were carefully uprooted from the polythene bag and data was collected on different root and shoot parameters.ANOVA was carried out for the whole data set using the SAS (version 9.2) statistical software.For those significant treatment mean differences, least significance difference (LSD) method was utilized (Montgomery, 2005).

RESULTS
The mean squares and the mean values per treatment for the various parameters measured are shown in table 1 and 2, respectively.As indicated in table 1, all the parameters considered in this experiment were significantly (P < 0.05) influenced by rooting media, except for cuttings with shoot and shoot length where the effect was nonsignificant.From the results of mean values (table 2), the highest percent (67.5) rooting ability of the softwood stem cuttings of the F 1 A rabica coffee hybrid was obtained when cuttings are grown on rooting media composed of 3Ts + 1S, followed by 64.17% of rooting recorded for cuttings propagated on media Ts+10cm Fw ss.However, the difference between the two media types was not significant.On the other hand, the lowest (49.17) percent rooting was obtained from media composed of 2Ts + 2S + 1M, though it is statistically at par with the percent rooting (53.34) recorded for rooting media mixes of 6Ts + 3S + 2M.
Similarly, effect of rooting media on percent callusing was significant where majority of cuttings were delayed in root formation when grown on media type 2Ts + 2S + 1M.The lowest on the contrary, was recorded for cuttings propagated on Ts+10cm Fw ss with average value of 28.34 per cent.Significantly different response of cuttings for number of roots and root length (cm) per cutting, were also observed for the media types.The highest root number and the longest root per cutting were recorded for cuttings grown on rooting media composed of Ts+10cm Fw ss, with mean values of 2.15 and 16.57cm, respectively.The influence of remaining media types on these parameters were non-significant except that the lowest values still are recorded from rooting media composed of 6Ts + 3S + 2M (1.62) and 2Ts + 2S + 1M (10.50 cm).
When above ground part is concerned, variation in media types did not show significant influence on shoot development and as well as shoot length per cutting.The highest number (100%) and the longest (4.40%) shoot were obtained for cuttings propagated on rooting media 2Ts + 2S + 1M.Shoot development and subsequent increase in length however, ranged from 98.15 to 100% and 3.91 to 4.40cm, respectively.The effect of rooting media on percent survival of cuttings on the other hand was highly significant.Total percent death of cuttings from the present study was recorded when 6Ts + 3S + 2M (10.83%) and Ts+10cm Fw ss (7.45%) were used as a rooting media.The least percent death (0.81) on the other hand, was recorded for cuttings propagated on 3Ts + 1S.

DISCUSSION
Significantly different influences of rooting media indicated that variable responses of cuttings of F1 Arabica coffee hybrids (Ababuna) to some media types for the parameters considered in these experiment.Accordingly, significantly higher percent of rooting coupled with lower percent of dead cuttings obtained from rooting media composed of 3Ts + 1S could generally be due to overall improvement in physical and chemical properties of the media which are associated with the balance between nutrient supply as well as optimal volume of pore spaces for proper drainage and adequate oxygen diffusion rate to satisfy the need of respiration and free from pathogen.These factors among others are crucial requirements for better survival, root initiation and subsequent growth of cuttings in vegetative propagation.Similarly, the higher percentage of rooting and root growth recorded for rooting media composed of Ts+10cm Fw ss could be associated with low pH of the sub soil filled top 10 cm.This result is similar with Wamatu and King'oro (1992) who have found conventional nursery media topped with 10 cm sub soil with better performance in rooting of Arabica coffee hybrid Ruiru 11 in Kenya.This indicates that acidic soil encourages root development from stem cuttings of Arabica coffee hybrid as it does for vegetative propagation through stem cuttings of tea clones (Coste, 1991).The acidic nature of sub soil might have played important role in loosening the cell wall of cuttings by increasing enzymatic activities involved in cell division, multiplication and specialization that facilitate early initiation of root primordial.However, relatively higher death of cuttings observed in this media could be related to low infiltration and aeration due to lack of coarse component in the potting mix which is basically used to improve drainage and aeration by increasing the proportion of large, air-filled pores.On the other hand, relatively higher death of cuttings observed in respect of the rooting media with manure could be due to infection of pathogen which might have contained in the manure.Rooting media composed of 2Ts + 2S + 1M which exhibited 89% percent rooting in the previous experiment (Behailu et al., 2004) had showed inferior performance in all parameter considered in these experiment.This could be due to change in physical properties of the media due to compaction when filling into polythene bags. www.gjournals.org65

CONCLUSION AND RECOMMENDATIONS
The result obtained from this experiment is a good indication of propagation of F1 Arabica coffee by rooting stem cuttings planted/inserted directly into polythene bags filled with appropriate rooting media using low cost propagating structures.Thus, it could be a better way of avoiding labor cost required to transplant the rooted cuttings to the pots and losses due to expected death of rooted cuttings during transplanting and subsequent hardening-off processes which is a common problem with mist system of propagation.Accordingly, it could be concluded that media composed of 3Ts +1S and Ts+10cm Fw ss could be recommended as potting media for better rooting and other root and shoot parameters for propagation of F1 Arabica coffee Ababuna by rooting soft wood stem cuttings.However, the sub soil needs to be mixed with certain rooting substrates such as sand to facilitate aeration and improve drainage for better survival of cuttings.Furthermore, intensive investigation including the remaining hybrids and focusing on other factor combination should be carried out through a continuative experiments to come up with conclusive recommendation, until successful rooting, above 90% is obtained.

Table 1 :
Mean square values for different root and shoot parameters recorded for stem cuttings of Aba-buna. ,* Indicates significant difference at 0.05 & 0.01 probability level, respectively.PR=percent rooting, PC= percent callusing, NR= number of roots per cutting, RL= root length, CWS= cuttings with soot, SL= shoot length and DC= dead cuttings. *

Table 2 :
Mean percent of rooting ability and other growth parameters of softwood stem cuttings of F 1 hybrid coffee planted in different potted media mixtures.Ts= top soil, S= sand, M= manure and Fwss= filled with subsoil.Values followed by the same letters are statistically similar.Numbers in the parenthesis are non-transformed values.PR=percent rooting, PC= percent callusing, NR= number of roots per cutting, RL= root length, CWS= cuttings with soot, SL= shoot length and DC= dead cuttings.